/**
 * @file
 * This is the IPv4 layer implementation for incoming and outgoing IP traffic.
 *
 * @see ip_frag.c
 *
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 */

#include "lwip/opt.h"

#if LWIP_IPV4

#include "lwip/ip.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/ip4_frag.h"
#include "lwip/inet_chksum.h"
#include "lwip/netif.h"
#include "lwip/icmp.h"
#include "lwip/igmp.h"
#include "lwip/raw.h"
#include "lwip/udp.h"
#include "lwip/priv/tcp_priv.h"
#include "lwip/autoip.h"
#include "lwip/stats.h"
#include "lwip/prot/dhcp.h"

#include <string.h>

#ifdef LWIP_HOOK_FILENAME
	#include LWIP_HOOK_FILENAME
#endif

/** Set this to 0 in the rare case of wanting to call an extra function to
 * generate the IP checksum (in contrast to calculating it on-the-fly). */
#ifndef LWIP_INLINE_IP_CHKSUM
	#if LWIP_CHECKSUM_CTRL_PER_NETIF
		#define LWIP_INLINE_IP_CHKSUM   0
	#else /* LWIP_CHECKSUM_CTRL_PER_NETIF */
		#define LWIP_INLINE_IP_CHKSUM   1
	#endif /* LWIP_CHECKSUM_CTRL_PER_NETIF */
#endif

#if LWIP_INLINE_IP_CHKSUM && CHECKSUM_GEN_IP
	#define CHECKSUM_GEN_IP_INLINE  1
#else
	#define CHECKSUM_GEN_IP_INLINE  0
#endif

#if LWIP_DHCP || defined(LWIP_IP_ACCEPT_UDP_PORT)
#define IP_ACCEPT_LINK_LAYER_ADDRESSING 1

/** Some defines for DHCP to let link-layer-addressed packets through while the
 * netif is down.
 * To use this in your own application/protocol, define LWIP_IP_ACCEPT_UDP_PORT(port)
 * to return 1 if the port is accepted and 0 if the port is not accepted.
 */
#if LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT)
/* accept DHCP client port and custom port */
#define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (((port) == PP_NTOHS(DHCP_CLIENT_PORT)) \
         || (LWIP_IP_ACCEPT_UDP_PORT(port)))
#elif defined(LWIP_IP_ACCEPT_UDP_PORT) /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
/* accept custom port only */
#define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (LWIP_IP_ACCEPT_UDP_PORT(port))
#else /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
/* accept DHCP client port only */
#define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) ((port) == PP_NTOHS(DHCP_CLIENT_PORT))
#endif /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */

#else /* LWIP_DHCP */
#define IP_ACCEPT_LINK_LAYER_ADDRESSING 0
#endif /* LWIP_DHCP */

/** The IP header ID of the next outgoing IP packet */
static u16_t ip_id;

#if LWIP_MULTICAST_TX_OPTIONS
/** The default netif used for multicast */
static struct netif* ip4_default_multicast_netif;

/**
 * @ingroup ip4
 * Set a default netif for IPv4 multicast. */
void
ip4_set_default_multicast_netif(struct netif* default_multicast_netif)
{
	ip4_default_multicast_netif = default_multicast_netif;
}
#endif /* LWIP_MULTICAST_TX_OPTIONS */

#ifdef LWIP_HOOK_IP4_ROUTE_SRC
/**
 * Source based IPv4 routing must be fully implemented in
 * LWIP_HOOK_IP4_ROUTE_SRC(). This function only provides he parameters.
 */
struct netif*
ip4_route_src(const ip4_addr_t* dest, const ip4_addr_t* src)
{
	if(src != NULL) {
		/* when src==NULL, the hook is called from ip4_route(dest) */
		struct netif* netif = LWIP_HOOK_IP4_ROUTE_SRC(dest, src);

		if(netif != NULL) {
			return netif;
		}
	}

	return ip4_route(dest);
}
#endif /* LWIP_HOOK_IP4_ROUTE_SRC */

/**
 * Finds the appropriate network interface for a given IP address. It
 * searches the list of network interfaces linearly. A match is found
 * if the masked IP address of the network interface equals the masked
 * IP address given to the function.
 *
 * @param dest the destination IP address for which to find the route
 * @return the netif on which to send to reach dest
 */
struct netif*
ip4_route(const ip4_addr_t* dest)
{
	struct netif* netif;

#if LWIP_MULTICAST_TX_OPTIONS

	/* Use administratively selected interface for multicast by default */
	if(ip4_addr_ismulticast(dest) && ip4_default_multicast_netif) {
		return ip4_default_multicast_netif;
	}

#endif /* LWIP_MULTICAST_TX_OPTIONS */

	/* iterate through netifs */
	for(netif = netif_list; netif != NULL; netif = netif->next) {
		/* is the netif up, does it have a link and a valid address? */
		if(netif_is_up(netif) && netif_is_link_up(netif) && !ip4_addr_isany_val(*netif_ip4_addr(netif))) {
			/* network mask matches? */
			if(ip4_addr_netcmp(dest, netif_ip4_addr(netif), netif_ip4_netmask(netif))) {
				/* return netif on which to forward IP packet */
				return netif;
			}

			/* gateway matches on a non broadcast interface? (i.e. peer in a point to point interface) */
			if(((netif->flags & NETIF_FLAG_BROADCAST) == 0) && ip4_addr_cmp(dest, netif_ip4_gw(netif))) {
				/* return netif on which to forward IP packet */
				return netif;
			}
		}
	}

#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF

	/* loopif is disabled, looopback traffic is passed through any netif */
	if(ip4_addr_isloopback(dest)) {
		/* don't check for link on loopback traffic */
		if(netif_default != NULL && netif_is_up(netif_default)) {
			return netif_default;
		}

		/* default netif is not up, just use any netif for loopback traffic */
		for(netif = netif_list; netif != NULL; netif = netif->next) {
			if(netif_is_up(netif)) {
				return netif;
			}
		}

		return NULL;
	}

#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */

#ifdef LWIP_HOOK_IP4_ROUTE_SRC
	netif = LWIP_HOOK_IP4_ROUTE_SRC(dest, NULL);

	if(netif != NULL) {
		return netif;
	}

#elif defined(LWIP_HOOK_IP4_ROUTE)
	netif = LWIP_HOOK_IP4_ROUTE(dest);

	if(netif != NULL) {
		return netif;
	}

#endif

	if((netif_default == NULL) || !netif_is_up(netif_default) || !netif_is_link_up(netif_default) ||
	        ip4_addr_isany_val(*netif_ip4_addr(netif_default))) {
		/* No matching netif found and default netif is not usable.
		   If this is not good enough for you, use LWIP_HOOK_IP4_ROUTE() */
		LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip4_route: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
		            ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
		IP_STATS_INC(ip.rterr);
		MIB2_STATS_INC(mib2.ipoutnoroutes);
		return NULL;
	}

	return netif_default;
}

#if IP_FORWARD
/**
 * Determine whether an IP address is in a reserved set of addresses
 * that may not be forwarded, or whether datagrams to that destination
 * may be forwarded.
 * @param p the packet to forward
 * @return 1: can forward 0: discard
 */
static int
ip4_canforward(struct pbuf* p)
{
	u32_t addr = lwip_htonl(ip4_addr_get_u32(ip4_current_dest_addr()));

	if(p->flags & PBUF_FLAG_LLBCAST) {
		/* don't route link-layer broadcasts */
		return 0;
	}

	if((p->flags & PBUF_FLAG_LLMCAST) && !IP_MULTICAST(addr)) {
		/* don't route link-layer multicasts unless the destination address is an IP
		   multicast address */
		return 0;
	}

	if(IP_EXPERIMENTAL(addr)) {
		return 0;
	}

	if(IP_CLASSA(addr)) {
		u32_t net = addr & IP_CLASSA_NET;

		if((net == 0) || (net == ((u32_t)IP_LOOPBACKNET << IP_CLASSA_NSHIFT))) {
			/* don't route loopback packets */
			return 0;
		}
	}

	return 1;
}

/**
 * Forwards an IP packet. It finds an appropriate route for the
 * packet, decrements the TTL value of the packet, adjusts the
 * checksum and outputs the packet on the appropriate interface.
 *
 * @param p the packet to forward (p->payload points to IP header)
 * @param iphdr the IP header of the input packet
 * @param inp the netif on which this packet was received
 */
static void
ip4_forward(struct pbuf* p, struct ip_hdr* iphdr, struct netif* inp)
{
	struct netif* netif;

	PERF_START;
	LWIP_UNUSED_ARG(inp);

	if(!ip4_canforward(p)) {
		goto return_noroute;
	}

	/* RFC3927 2.7: do not forward link-local addresses */
	if(ip4_addr_islinklocal(ip4_current_dest_addr())) {
		LWIP_DEBUGF(IP_DEBUG, ("ip4_forward: not forwarding LLA %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
		                       ip4_addr1_16(ip4_current_dest_addr()), ip4_addr2_16(ip4_current_dest_addr()),
		                       ip4_addr3_16(ip4_current_dest_addr()), ip4_addr4_16(ip4_current_dest_addr())));
		goto return_noroute;
	}

	/* Find network interface where to forward this IP packet to. */
	netif = ip4_route_src(ip4_current_dest_addr(), ip4_current_src_addr());

	if(netif == NULL) {
		LWIP_DEBUGF(IP_DEBUG, ("ip4_forward: no forwarding route for %"U16_F".%"U16_F".%"U16_F".%"U16_F" found\n",
		                       ip4_addr1_16(ip4_current_dest_addr()), ip4_addr2_16(ip4_current_dest_addr()),
		                       ip4_addr3_16(ip4_current_dest_addr()), ip4_addr4_16(ip4_current_dest_addr())));
		/* @todo: send ICMP_DUR_NET? */
		goto return_noroute;
	}

#if !IP_FORWARD_ALLOW_TX_ON_RX_NETIF

	/* Do not forward packets onto the same network interface on which
	 * they arrived. */
	if(netif == inp) {
		LWIP_DEBUGF(IP_DEBUG, ("ip4_forward: not bouncing packets back on incoming interface.\n"));
		goto return_noroute;
	}

#endif /* IP_FORWARD_ALLOW_TX_ON_RX_NETIF */

	/* decrement TTL */
	IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);

	/* send ICMP if TTL == 0 */
	if(IPH_TTL(iphdr) == 0) {
		MIB2_STATS_INC(mib2.ipinhdrerrors);
#if LWIP_ICMP

		/* Don't send ICMP messages in response to ICMP messages */
		if(IPH_PROTO(iphdr) != IP_PROTO_ICMP) {
			icmp_time_exceeded(p, ICMP_TE_TTL);
		}

#endif /* LWIP_ICMP */
		return;
	}

	/* Incrementally update the IP checksum. */
	if(IPH_CHKSUM(iphdr) >= PP_HTONS(0xffffU - 0x100)) {
		IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + PP_HTONS(0x100) + 1);
	} else {
		IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + PP_HTONS(0x100));
	}

	LWIP_DEBUGF(IP_DEBUG, ("ip4_forward: forwarding packet to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
	                       ip4_addr1_16(ip4_current_dest_addr()), ip4_addr2_16(ip4_current_dest_addr()),
	                       ip4_addr3_16(ip4_current_dest_addr()), ip4_addr4_16(ip4_current_dest_addr())));

	IP_STATS_INC(ip.fw);
	MIB2_STATS_INC(mib2.ipforwdatagrams);
	IP_STATS_INC(ip.xmit);

	PERF_STOP("ip4_forward");

	/* don't fragment if interface has mtu set to 0 [loopif] */
	if(netif->mtu && (p->tot_len > netif->mtu)) {
		if((IPH_OFFSET(iphdr) & PP_NTOHS(IP_DF)) == 0) {
#if IP_FRAG
			ip4_frag(p, netif, ip4_current_dest_addr());
#else /* IP_FRAG */
			/* @todo: send ICMP Destination Unreachable code 13 "Communication administratively prohibited"? */
#endif /* IP_FRAG */
		} else {
#if LWIP_ICMP
			/* send ICMP Destination Unreachable code 4: "Fragmentation Needed and DF Set" */
			icmp_dest_unreach(p, ICMP_DUR_FRAG);
#endif /* LWIP_ICMP */
		}

		return;
	}

	/* transmit pbuf on chosen interface */
	netif->output(netif, p, ip4_current_dest_addr());
	return;
return_noroute:
	MIB2_STATS_INC(mib2.ipoutnoroutes);
}
#endif /* IP_FORWARD */

/**
 * This function is called by the network interface device driver when
 * an IP packet is received. The function does the basic checks of the
 * IP header such as packet size being at least larger than the header
 * size etc. If the packet was not destined for us, the packet is
 * forwarded (using ip_forward). The IP checksum is always checked.
 *
 * Finally, the packet is sent to the upper layer protocol input function.
 *
 * @param p the received IP packet (p->payload points to IP header)
 * @param inp the netif on which this packet was received
 * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't
 *         processed, but currently always returns ERR_OK)
 */
err_t
ip4_input(struct pbuf* p, struct netif* inp)
{
	struct ip_hdr* iphdr;
	struct netif* netif;
	u16_t iphdr_hlen;
	u16_t iphdr_len;
#if IP_ACCEPT_LINK_LAYER_ADDRESSING || LWIP_IGMP
	int check_ip_src = 1;
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING || LWIP_IGMP */

	IP_STATS_INC(ip.recv);
	MIB2_STATS_INC(mib2.ipinreceives);

	/* identify the IP header */
	iphdr = (struct ip_hdr*)p->payload;

	if(IPH_V(iphdr) != 4) {
		LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", (u16_t)IPH_V(iphdr)));
		ip4_debug_print(p);
		pbuf_free(p);
		IP_STATS_INC(ip.err);
		IP_STATS_INC(ip.drop);
		MIB2_STATS_INC(mib2.ipinhdrerrors);
		return ERR_OK;
	}

#ifdef LWIP_HOOK_IP4_INPUT

	if(LWIP_HOOK_IP4_INPUT(p, inp)) {
		/* the packet has been eaten */
		return ERR_OK;
	}

#endif

	/* obtain IP header length in number of 32-bit words */
	iphdr_hlen = IPH_HL(iphdr);
	/* calculate IP header length in bytes */
	iphdr_hlen *= 4;
	/* obtain ip length in bytes */
	iphdr_len = lwip_ntohs(IPH_LEN(iphdr));

	/* Trim pbuf. This is especially required for packets < 60 bytes. */
	if(iphdr_len < p->tot_len) {
		pbuf_realloc(p, iphdr_len);
	}

	/* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
	if((iphdr_hlen > p->len) || (iphdr_len > p->tot_len) || (iphdr_hlen < IP_HLEN)) {
		if(iphdr_hlen < IP_HLEN) {
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("ip4_input: short IP header (%"U16_F" bytes) received, IP packet dropped\n", iphdr_hlen));
		}

		if(iphdr_hlen > p->len) {
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
			             iphdr_hlen, p->len));
		}

		if(iphdr_len > p->tot_len) {
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
			             iphdr_len, p->tot_len));
		}

		/* free (drop) packet pbufs */
		pbuf_free(p);
		IP_STATS_INC(ip.lenerr);
		IP_STATS_INC(ip.drop);
		MIB2_STATS_INC(mib2.ipindiscards);
		return ERR_OK;
	}

	/* verify checksum */
#if CHECKSUM_CHECK_IP
	IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_IP) {
		if(inet_chksum(iphdr, iphdr_hlen) != 0) {

			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
			            ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
			ip4_debug_print(p);
			pbuf_free(p);
			IP_STATS_INC(ip.chkerr);
			IP_STATS_INC(ip.drop);
			MIB2_STATS_INC(mib2.ipinhdrerrors);
			return ERR_OK;
		}
	}
#endif

	/* copy IP addresses to aligned ip_addr_t */
	ip_addr_copy_from_ip4(ip_data.current_iphdr_dest, iphdr->dest);
	ip_addr_copy_from_ip4(ip_data.current_iphdr_src, iphdr->src);

	/* match packet against an interface, i.e. is this packet for us? */
	if(ip4_addr_ismulticast(ip4_current_dest_addr())) {
#if LWIP_IGMP

		if((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, ip4_current_dest_addr()))) {
			/* IGMP snooping switches need 0.0.0.0 to be allowed as source address (RFC 4541) */
			ip4_addr_t allsystems;
			IP4_ADDR(&allsystems, 224, 0, 0, 1);

			if(ip4_addr_cmp(ip4_current_dest_addr(), &allsystems) &&
			        ip4_addr_isany(ip4_current_src_addr())) {
				check_ip_src = 0;
			}

			netif = inp;
		} else {
			netif = NULL;
		}

#else /* LWIP_IGMP */

		if((netif_is_up(inp)) && (!ip4_addr_isany_val(*netif_ip4_addr(inp)))) {
			netif = inp;
		} else {
			netif = NULL;
		}

#endif /* LWIP_IGMP */
	} else {
		/* start trying with inp. if that's not acceptable, start walking the
		   list of configured netifs.
		   'first' is used as a boolean to mark whether we started walking the list */
		int first = 1;
		netif = inp;

		do {
			LWIP_DEBUGF(IP_DEBUG, ("ip_input: iphdr->dest 0x%"X32_F" netif->ip_addr 0x%"X32_F" (0x%"X32_F", 0x%"X32_F", 0x%"X32_F")\n",
			                       ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(netif_ip4_addr(netif)),
			                       ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(netif_ip4_netmask(netif)),
			                       ip4_addr_get_u32(netif_ip4_addr(netif)) & ip4_addr_get_u32(netif_ip4_netmask(netif)),
			                       ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(netif_ip4_netmask(netif))));

			/* interface is up and configured? */
			if((netif_is_up(netif)) && (!ip4_addr_isany_val(*netif_ip4_addr(netif)))) {
				/* unicast to this interface address? */
				if(ip4_addr_cmp(ip4_current_dest_addr(), netif_ip4_addr(netif)) ||
				        /* or broadcast on this interface network address? */
				        ip4_addr_isbroadcast(ip4_current_dest_addr(), netif)
#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
				        || (ip4_addr_get_u32(ip4_current_dest_addr()) == PP_HTONL(IPADDR_LOOPBACK))
#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
				  ) {
					LWIP_DEBUGF(IP_DEBUG, ("ip4_input: packet accepted on interface %c%c\n",
					                       netif->name[0], netif->name[1]));
					/* break out of for loop */
					break;
				}

#if LWIP_AUTOIP

				/* connections to link-local addresses must persist after changing
				   the netif's address (RFC3927 ch. 1.9) */
				if(autoip_accept_packet(netif, ip4_current_dest_addr())) {
					LWIP_DEBUGF(IP_DEBUG, ("ip4_input: LLA packet accepted on interface %c%c\n",
					                       netif->name[0], netif->name[1]));
					/* break out of for loop */
					break;
				}

#endif /* LWIP_AUTOIP */
			}

			if(first) {
#if !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF

				/* Packets sent to the loopback address must not be accepted on an
				 * interface that does not have the loopback address assigned to it,
				 * unless a non-loopback interface is used for loopback traffic. */
				if(ip4_addr_isloopback(ip4_current_dest_addr())) {
					netif = NULL;
					break;
				}

#endif /* !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF */
				first = 0;
				netif = netif_list;
			} else {
				netif = netif->next;
			}

			if(netif == inp) {
				netif = netif->next;
			}
		} while(netif != NULL);
	}

#if IP_ACCEPT_LINK_LAYER_ADDRESSING

	/* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
	 * using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
	 * According to RFC 1542 section 3.1.1, referred by RFC 2131).
	 *
	 * If you want to accept private broadcast communication while a netif is down,
	 * define LWIP_IP_ACCEPT_UDP_PORT(dst_port), e.g.:
	 *
	 * #define LWIP_IP_ACCEPT_UDP_PORT(dst_port) ((dst_port) == PP_NTOHS(12345))
	 */
	if(netif == NULL) {
		/* remote port is DHCP server? */
		if(IPH_PROTO(iphdr) == IP_PROTO_UDP) {
			struct udp_hdr* udphdr = (struct udp_hdr*)((u8_t*)iphdr + iphdr_hlen);
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: UDP packet to DHCP client port %"U16_F"\n",
			                                        lwip_ntohs(udphdr->dest)));

			if(IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(udphdr->dest)) {
				LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: DHCP packet accepted.\n"));
				netif = inp;
				check_ip_src = 0;
			}
		}
	}

#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */

	/* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
#if LWIP_IGMP || IP_ACCEPT_LINK_LAYER_ADDRESSING

	if(check_ip_src
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
	        /* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
	        && !ip4_addr_isany_val(*ip4_current_src_addr())
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
	  )
#endif /* LWIP_IGMP || IP_ACCEPT_LINK_LAYER_ADDRESSING */
	{
		if((ip4_addr_isbroadcast(ip4_current_src_addr(), inp)) ||
		        (ip4_addr_ismulticast(ip4_current_src_addr()))) {
			/* packet source is not valid */
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip4_input: packet source is not valid.\n"));
			/* free (drop) packet pbufs */
			pbuf_free(p);
			IP_STATS_INC(ip.drop);
			MIB2_STATS_INC(mib2.ipinaddrerrors);
			MIB2_STATS_INC(mib2.ipindiscards);
			return ERR_OK;
		}
	}

	/* packet not for us? */
	if(netif == NULL) {
		/* packet not for us, route or discard */
		LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: packet not for us.\n"));
#if IP_FORWARD

		/* non-broadcast packet? */
		if(!ip4_addr_isbroadcast(ip4_current_dest_addr(), inp)) {
			/* try to forward IP packet on (other) interfaces */
			ip4_forward(p, iphdr, inp);
		} else
#endif /* IP_FORWARD */
		{
			IP_STATS_INC(ip.drop);
			MIB2_STATS_INC(mib2.ipinaddrerrors);
			MIB2_STATS_INC(mib2.ipindiscards);
		}

		pbuf_free(p);
		return ERR_OK;
	}

	/* packet consists of multiple fragments? */
	if((IPH_OFFSET(iphdr) & PP_HTONS(IP_OFFMASK | IP_MF)) != 0) {
#if IP_REASSEMBLY /* packet fragment reassembly code present? */
		LWIP_DEBUGF(IP_DEBUG, ("IP packet is a fragment (id=0x%04"X16_F" tot_len=%"U16_F" len=%"U16_F" MF=%"U16_F" offset=%"U16_F"), calling ip4_reass()\n",
		                       lwip_ntohs(IPH_ID(iphdr)), p->tot_len, lwip_ntohs(IPH_LEN(iphdr)), (u16_t)!!(IPH_OFFSET(iphdr) & PP_HTONS(IP_MF)), (u16_t)((lwip_ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK) * 8)));
		/* reassemble the packet*/
		p = ip4_reass(p);

		/* packet not fully reassembled yet? */
		if(p == NULL) {
			return ERR_OK;
		}

		iphdr = (struct ip_hdr*)p->payload;
#else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
		pbuf_free(p);
		LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
		            lwip_ntohs(IPH_OFFSET(iphdr))));
		IP_STATS_INC(ip.opterr);
		IP_STATS_INC(ip.drop);
		/* unsupported protocol feature */
		MIB2_STATS_INC(mib2.ipinunknownprotos);
		return ERR_OK;
#endif /* IP_REASSEMBLY */
	}

#if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */

#if LWIP_IGMP

	/* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
	if((iphdr_hlen > IP_HLEN) && (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
#else

	if(iphdr_hlen > IP_HLEN) {
#endif /* LWIP_IGMP */
		LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
		pbuf_free(p);
		IP_STATS_INC(ip.opterr);
		IP_STATS_INC(ip.drop);
		/* unsupported protocol feature */
		MIB2_STATS_INC(mib2.ipinunknownprotos);
		return ERR_OK;
	}

#endif /* IP_OPTIONS_ALLOWED == 0 */

	/* send to upper layers */
	LWIP_DEBUGF(IP_DEBUG, ("ip4_input: \n"));
	ip4_debug_print(p);
	LWIP_DEBUGF(IP_DEBUG, ("ip4_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));

	ip_data.current_netif = netif;
	ip_data.current_input_netif = inp;
	ip_data.current_ip4_header = iphdr;
	ip_data.current_ip_header_tot_len = IPH_HL(iphdr) * 4;

#if LWIP_RAW

	/* raw input did not eat the packet? */
	if(raw_input(p, inp) == 0)
#endif /* LWIP_RAW */
	{
		pbuf_header(p, -(s16_t)iphdr_hlen); /* Move to payload, no check necessary. */

		switch(IPH_PROTO(iphdr)) {
#if LWIP_UDP

			case IP_PROTO_UDP:
#if LWIP_UDPLITE
			case IP_PROTO_UDPLITE:
#endif /* LWIP_UDPLITE */
				MIB2_STATS_INC(mib2.ipindelivers);
				udp_input(p, inp);
				break;
#endif /* LWIP_UDP */
#if LWIP_TCP

			case IP_PROTO_TCP:
				MIB2_STATS_INC(mib2.ipindelivers);
				tcp_input(p, inp);
				break;
#endif /* LWIP_TCP */
#if LWIP_ICMP

			case IP_PROTO_ICMP:
				MIB2_STATS_INC(mib2.ipindelivers);
				icmp_input(p, inp);
				break;
#endif /* LWIP_ICMP */
#if LWIP_IGMP

			case IP_PROTO_IGMP:
				igmp_input(p, inp, ip4_current_dest_addr());
				break;
#endif /* LWIP_IGMP */

			default:
#if LWIP_ICMP

				/* send ICMP destination protocol unreachable unless is was a broadcast */
				if(!ip4_addr_isbroadcast(ip4_current_dest_addr(), netif) &&
				        !ip4_addr_ismulticast(ip4_current_dest_addr())) {
					pbuf_header_force(p, iphdr_hlen); /* Move to ip header, no check necessary. */
					p->payload = iphdr;
					icmp_dest_unreach(p, ICMP_DUR_PROTO);
				}

#endif /* LWIP_ICMP */
				pbuf_free(p);

				LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", (u16_t)IPH_PROTO(iphdr)));

				IP_STATS_INC(ip.proterr);
				IP_STATS_INC(ip.drop);
				MIB2_STATS_INC(mib2.ipinunknownprotos);
		}
	}

	/* @todo: this is not really necessary... */
	ip_data.current_netif = NULL;
	ip_data.current_input_netif = NULL;
	ip_data.current_ip4_header = NULL;
	ip_data.current_ip_header_tot_len = 0;
	ip4_addr_set_any(ip4_current_src_addr());
	ip4_addr_set_any(ip4_current_dest_addr());

	return ERR_OK;
}

/**
 * Sends an IP packet on a network interface. This function constructs
 * the IP header and calculates the IP header checksum. If the source
 * IP address is NULL, the IP address of the outgoing network
 * interface is filled in as source address.
 * If the destination IP address is LWIP_IP_HDRINCL, p is assumed to already
 * include an IP header and p->payload points to it instead of the data.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IP header and p->payload points to that IP header)
 * @param src the source IP address to send from (if src == IP4_ADDR_ANY, the
 *         IP  address of the netif used to send is used as source address)
 * @param dest the destination IP address to send the packet to
 * @param ttl the TTL value to be set in the IP header
 * @param tos the TOS value to be set in the IP header
 * @param proto the PROTOCOL to be set in the IP header
 * @param netif the netif on which to send this packet
 * @return ERR_OK if the packet was sent OK
 *         ERR_BUF if p doesn't have enough space for IP/LINK headers
 *         returns errors returned by netif->output
 *
 * @note ip_id: RFC791 "some host may be able to simply use
 *  unique identifiers independent of destination"
 */
err_t
ip4_output_if(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
              u8_t ttl, u8_t tos,
              u8_t proto, struct netif* netif)
{
#if IP_OPTIONS_SEND
	return ip4_output_if_opt(p, src, dest, ttl, tos, proto, netif, NULL, 0);
}

/**
 * Same as ip_output_if() but with the possibility to include IP options:
 *
 * @ param ip_options pointer to the IP options, copied into the IP header
 * @ param optlen length of ip_options
 */
err_t
ip4_output_if_opt(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
                  u8_t ttl, u8_t tos, u8_t proto, struct netif* netif, void* ip_options,
                  u16_t optlen)
{
#endif /* IP_OPTIONS_SEND */
	const ip4_addr_t* src_used = src;

	if(dest != LWIP_IP_HDRINCL) {
		if(ip4_addr_isany(src)) {
			src_used = netif_ip4_addr(netif);
		}
	}

#if IP_OPTIONS_SEND
	return ip4_output_if_opt_src(p, src_used, dest, ttl, tos, proto, netif,
	                             ip_options, optlen);
#else /* IP_OPTIONS_SEND */
	return ip4_output_if_src(p, src_used, dest, ttl, tos, proto, netif);
#endif /* IP_OPTIONS_SEND */
}

/**
 * Same as ip_output_if() but 'src' address is not replaced by netif address
 * when it is 'any'.
 */
err_t
ip4_output_if_src(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
                  u8_t ttl, u8_t tos,
                  u8_t proto, struct netif* netif)
{
#if IP_OPTIONS_SEND
	return ip4_output_if_opt_src(p, src, dest, ttl, tos, proto, netif, NULL, 0);
}

/**
 * Same as ip_output_if_opt() but 'src' address is not replaced by netif address
 * when it is 'any'.
 */
err_t
ip4_output_if_opt_src(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
                      u8_t ttl, u8_t tos, u8_t proto, struct netif* netif, void* ip_options,
                      u16_t optlen)
{
#endif /* IP_OPTIONS_SEND */
	struct ip_hdr* iphdr;
	ip4_addr_t dest_addr;
#if CHECKSUM_GEN_IP_INLINE
	u32_t chk_sum = 0;
#endif /* CHECKSUM_GEN_IP_INLINE */

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	MIB2_STATS_INC(mib2.ipoutrequests);

	/* Should the IP header be generated or is it already included in p? */
	if(dest != LWIP_IP_HDRINCL) {
		u16_t ip_hlen = IP_HLEN;
#if IP_OPTIONS_SEND
		u16_t optlen_aligned = 0;

		if(optlen != 0) {
#if CHECKSUM_GEN_IP_INLINE
			int i;
#endif /* CHECKSUM_GEN_IP_INLINE */
			/* round up to a multiple of 4 */
			optlen_aligned = ((optlen + 3) & ~3);
			ip_hlen += optlen_aligned;

			/* First write in the IP options */
			if(pbuf_header(p, optlen_aligned)) {
				LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip4_output_if_opt: not enough room for IP options in pbuf\n"));
				IP_STATS_INC(ip.err);
				MIB2_STATS_INC(mib2.ipoutdiscards);
				return ERR_BUF;
			}

			MEMCPY(p->payload, ip_options, optlen);

			if(optlen < optlen_aligned) {
				/* zero the remaining bytes */
				memset(((char*)p->payload) + optlen, 0, optlen_aligned - optlen);
			}

#if CHECKSUM_GEN_IP_INLINE

			for(i = 0; i < optlen_aligned / 2; i++) {
				chk_sum += ((u16_t*)p->payload)[i];
			}

#endif /* CHECKSUM_GEN_IP_INLINE */
		}

#endif /* IP_OPTIONS_SEND */

		/* generate IP header */
		if(pbuf_header(p, IP_HLEN)) {
			LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip4_output: not enough room for IP header in pbuf\n"));

			IP_STATS_INC(ip.err);
			MIB2_STATS_INC(mib2.ipoutdiscards);
			return ERR_BUF;
		}

		iphdr = (struct ip_hdr*)p->payload;
		LWIP_ASSERT("check that first pbuf can hold struct ip_hdr",
		            (p->len >= sizeof(struct ip_hdr)));

		IPH_TTL_SET(iphdr, ttl);
		IPH_PROTO_SET(iphdr, proto);
#if CHECKSUM_GEN_IP_INLINE
		chk_sum += PP_NTOHS(proto | (ttl << 8));
#endif /* CHECKSUM_GEN_IP_INLINE */

		/* dest cannot be NULL here */
		ip4_addr_copy(iphdr->dest, *dest);
#if CHECKSUM_GEN_IP_INLINE
		chk_sum += ip4_addr_get_u32(&iphdr->dest) & 0xFFFF;
		chk_sum += ip4_addr_get_u32(&iphdr->dest) >> 16;
#endif /* CHECKSUM_GEN_IP_INLINE */

		IPH_VHL_SET(iphdr, 4, ip_hlen / 4);
		IPH_TOS_SET(iphdr, tos);
#if CHECKSUM_GEN_IP_INLINE
		chk_sum += PP_NTOHS(tos | (iphdr->_v_hl << 8));
#endif /* CHECKSUM_GEN_IP_INLINE */
		IPH_LEN_SET(iphdr, lwip_htons(p->tot_len));
#if CHECKSUM_GEN_IP_INLINE
		chk_sum += iphdr->_len;
#endif /* CHECKSUM_GEN_IP_INLINE */
		IPH_OFFSET_SET(iphdr, 0);
		IPH_ID_SET(iphdr, lwip_htons(ip_id));
#if CHECKSUM_GEN_IP_INLINE
		chk_sum += iphdr->_id;
#endif /* CHECKSUM_GEN_IP_INLINE */
		++ip_id;

		if(src == NULL) {
			ip4_addr_copy(iphdr->src, *IP4_ADDR_ANY4);
		} else {
			/* src cannot be NULL here */
			ip4_addr_copy(iphdr->src, *src);
		}

#if CHECKSUM_GEN_IP_INLINE
		chk_sum += ip4_addr_get_u32(&iphdr->src) & 0xFFFF;
		chk_sum += ip4_addr_get_u32(&iphdr->src) >> 16;
		chk_sum = (chk_sum >> 16) + (chk_sum & 0xFFFF);
		chk_sum = (chk_sum >> 16) + chk_sum;
		chk_sum = ~chk_sum;
		IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_IP) {
			iphdr->_chksum = (u16_t)chk_sum; /* network order */
		}
#if LWIP_CHECKSUM_CTRL_PER_NETIF
		else {
			IPH_CHKSUM_SET(iphdr, 0);
		}

#endif /* LWIP_CHECKSUM_CTRL_PER_NETIF*/
#else /* CHECKSUM_GEN_IP_INLINE */
		IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
		IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_IP) {
			IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, ip_hlen));
		}
#endif /* CHECKSUM_GEN_IP */
#endif /* CHECKSUM_GEN_IP_INLINE */
	} else {
		/* IP header already included in p */
		iphdr = (struct ip_hdr*)p->payload;
		ip4_addr_copy(dest_addr, iphdr->dest);
		dest = &dest_addr;
	}

	IP_STATS_INC(ip.xmit);

	LWIP_DEBUGF(IP_DEBUG, ("ip4_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], (u16_t)netif->num));
	ip4_debug_print(p);

#if ENABLE_LOOPBACK

	if(ip4_addr_cmp(dest, netif_ip4_addr(netif))
#if !LWIP_HAVE_LOOPIF
	        || ip4_addr_isloopback(dest)
#endif /* !LWIP_HAVE_LOOPIF */
	  ) {
		/* Packet to self, enqueue it for loopback */
		LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));
		return netif_loop_output(netif, p);
	}

#if LWIP_MULTICAST_TX_OPTIONS

	if((p->flags & PBUF_FLAG_MCASTLOOP) != 0) {
		netif_loop_output(netif, p);
	}

#endif /* LWIP_MULTICAST_TX_OPTIONS */
#endif /* ENABLE_LOOPBACK */
#if IP_FRAG

	/* don't fragment if interface has mtu set to 0 [loopif] */
	if(netif->mtu && (p->tot_len > netif->mtu)) {
		return ip4_frag(p, netif, dest);
	}

#endif /* IP_FRAG */

	LWIP_DEBUGF(IP_DEBUG, ("ip4_output_if: call netif->output()\n"));
	return netif->output(netif, p, dest);
}

/**
 * Simple interface to ip_output_if. It finds the outgoing network
 * interface and calls upon ip_output_if to do the actual work.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IP header and p->payload points to that IP header)
 * @param src the source IP address to send from (if src == IP4_ADDR_ANY, the
 *         IP  address of the netif used to send is used as source address)
 * @param dest the destination IP address to send the packet to
 * @param ttl the TTL value to be set in the IP header
 * @param tos the TOS value to be set in the IP header
 * @param proto the PROTOCOL to be set in the IP header
 *
 * @return ERR_RTE if no route is found
 *         see ip_output_if() for more return values
 */
err_t
ip4_output(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
           u8_t ttl, u8_t tos, u8_t proto)
{
	struct netif* netif;

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	if((netif = ip4_route_src(dest, src)) == NULL) {
		LWIP_DEBUGF(IP_DEBUG, ("ip4_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
		                       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
		IP_STATS_INC(ip.rterr);
		return ERR_RTE;
	}

	return ip4_output_if(p, src, dest, ttl, tos, proto, netif);
}

#if LWIP_NETIF_HWADDRHINT
/** Like ip_output, but takes and addr_hint pointer that is passed on to netif->addr_hint
 *  before calling ip_output_if.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
            IP header and p->payload points to that IP header)
 * @param src the source IP address to send from (if src == IP4_ADDR_ANY, the
 *         IP  address of the netif used to send is used as source address)
 * @param dest the destination IP address to send the packet to
 * @param ttl the TTL value to be set in the IP header
 * @param tos the TOS value to be set in the IP header
 * @param proto the PROTOCOL to be set in the IP header
 * @param addr_hint address hint pointer set to netif->addr_hint before
 *        calling ip_output_if()
 *
 * @return ERR_RTE if no route is found
 *         see ip_output_if() for more return values
 */
err_t
ip4_output_hinted(struct pbuf* p, const ip4_addr_t* src, const ip4_addr_t* dest,
                  u8_t ttl, u8_t tos, u8_t proto, u8_t* addr_hint)
{
	struct netif* netif;
	err_t err;

	LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);

	if((netif = ip4_route_src(dest, src)) == NULL) {
		LWIP_DEBUGF(IP_DEBUG, ("ip4_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
		                       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
		IP_STATS_INC(ip.rterr);
		return ERR_RTE;
	}

	NETIF_SET_HWADDRHINT(netif, addr_hint);
	err = ip4_output_if(p, src, dest, ttl, tos, proto, netif);
	NETIF_SET_HWADDRHINT(netif, NULL);

	return err;
}
#endif /* LWIP_NETIF_HWADDRHINT*/

#if IP_DEBUG
/* Print an IP header by using LWIP_DEBUGF
 * @param p an IP packet, p->payload pointing to the IP header
 */
void
ip4_debug_print(struct pbuf* p)
{
	struct ip_hdr* iphdr = (struct ip_hdr*)p->payload;

	LWIP_DEBUGF(IP_DEBUG, ("IP header:\n"));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP_DEBUG, ("|%2"S16_F" |%2"S16_F" |  0x%02"X16_F" |     %5"U16_F"     | (v, hl, tos, len)\n",
	                       (u16_t)IPH_V(iphdr),
	                       (u16_t)IPH_HL(iphdr),
	                       (u16_t)IPH_TOS(iphdr),
	                       lwip_ntohs(IPH_LEN(iphdr))));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP_DEBUG, ("|    %5"U16_F"      |%"U16_F"%"U16_F"%"U16_F"|    %4"U16_F"   | (id, flags, offset)\n",
	                       lwip_ntohs(IPH_ID(iphdr)),
	                       (u16_t)(lwip_ntohs(IPH_OFFSET(iphdr)) >> 15 & 1),
	                       (u16_t)(lwip_ntohs(IPH_OFFSET(iphdr)) >> 14 & 1),
	                       (u16_t)(lwip_ntohs(IPH_OFFSET(iphdr)) >> 13 & 1),
	                       (u16_t)(lwip_ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |    0x%04"X16_F"     | (ttl, proto, chksum)\n",
	                       (u16_t)IPH_TTL(iphdr),
	                       (u16_t)IPH_PROTO(iphdr),
	                       lwip_ntohs(IPH_CHKSUM(iphdr))));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (src)\n",
	                       ip4_addr1_16(&iphdr->src),
	                       ip4_addr2_16(&iphdr->src),
	                       ip4_addr3_16(&iphdr->src),
	                       ip4_addr4_16(&iphdr->src)));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
	LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (dest)\n",
	                       ip4_addr1_16(&iphdr->dest),
	                       ip4_addr2_16(&iphdr->dest),
	                       ip4_addr3_16(&iphdr->dest),
	                       ip4_addr4_16(&iphdr->dest)));
	LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
}
#endif /* IP_DEBUG */

#endif /* LWIP_IPV4 */
